This invention relates to an exposure apparatus used to manufacture a semiconductor device or the like by exposing a resist on a substrate to a design pattern, a method of manufacturing devices using this exposure apparatus, and a stage device and reference-position return method applicable to this apparatus and method.
Examples of such exposure apparatus generally used to manufacture semiconductor devices include a stepper which sequentially exposes a plurality of exposure areas on a substrate such as a wafer to a pattern on a reticle via a projecting optical system while the substrate is moved in steps, and a scanning-type exposure apparatus which moves a reticle such as a mask and a substrate relative to a projecting optical system and scans the reticle and the substrate by slit-shaped exposing light to thereby expose the substrate to the pattern on the reticle by scanning.
A step-and-scan-type exposure apparatus has been proposed in recent years. This apparatus exposes a plurality of areas on a substrate to a fine pattern in a highly precise fashion by repeating the above-mentioned stepping motion and scanning exposure in such a manner that exposure of a fine pattern can be carried out with greater accuracy. This exposure apparatus is so adapted that exposing light is limited by a slit so that only a portion of the light comparatively near the optical axis of the projecting optical system is used. This makes possible the exposure of a fine pattern with improved accuracy.
However, a problem with the conventional exposure apparatus is that the positioning accuracy of the substrate exposed to light and the accuracy of movement in the scanning direction are not adequate, to achieve exposure of the fine patterns at the high precision mentioned above.
A precision stage capable of being driven along a plurality of axes is provided in the above-described exposure apparatus in order to make possible the fine positioning of the stage that carries the substrate. In general, the precision stage is capable of fine movement along the Z axis, which coincides with the direction of the optical axis of the exposing light, along a direction inclined with respect to the Z axis, and in a direction of rotation about the Z axis.
Since the precision stage has a plurality of axes along which it is driven, however, this makes it much more difficult to return the precision stage to its reference position accurately. Measuring the position of the stage accurately by laser interferometty or the like cannot be carried out and accuracy of movement cannot be maintained at a high level unless the precision stage is returned to its reference position accurately.